Laxatives Flashcards
Laxative
Soft but formed stool
Cathartic
Watery not formed stool
Causes of constipation
Narcotics, clonidine, antacids (mg/po4), iron, barium, hypothyroid
Constipation TX
Non-pharm best - 20-25 g/d fiber
-good fluid intake - 4-6 cups
Bulk forming
Primary TX
Psyllium, fiber, methylcellulose, polycarbophil
MOA - absorb and retain water, increases fecal volume, soften stool, increase rate of transit
Forms gas due to bacterial degradation
Good in pts with constipation/diarrhea
SE - loss of water/lytes, decreased vitamin absorption (binds RX)
Gentle but slow
Saline
2nd choice
MOM, mgso4, macitrate, naphos
Non-absorbable ions
Small doses - laxative
Large doses - cathartic
MOA - osmotically draws water into GI
-some suppositories produce CO2
Use - routine GI (entire) emptying
-removal of impaction
SE - lytes abnormalities, dehydration, excess mg
-naphos in high amts can cause acute phos nephrotox
Lactulose
Gentle but $$$
Poorly absorbed sugar
Use - acidification of feces inccreases ammonia excretion and provides symptomatic relief of portal-systemic encephalopathy (PSE)
Sorbitol, prune juice
Like lactulose but less $
Undergoes bacterial fermentation - gas, bloated feeling
PEG, glycerine
PEG onset - 2-4 days
Glycerine (peds) - 15-30 min
Stimulant Laxatives
3rd line
Often abused
MOA - increased peristalsis and increased fluid accumulation
-effect in 2-6 hrs
SE - lytes imbalance, colored urine
Use - constipation that doesn’t respond to bulk or osmotic laxatives
-empty GI tract
Bisacodyl
Stimulant laxative
Variable efficacy per person
Enema contains tannic acid which is hepatotoxic
Used for colon prep surgery
Caution with repeated use
Lubiprostone
Bicyclic fatty acid related to PGE1 - activates Cl channels and moves Cl into intestinal lumen – increases fluid secretion and motility
Can be used for chronic idiopathic constipation due to low risk for tolerance
- also approved for IBS in women
Tegaserod
Prokinetic agent - 5HT agonist
- indirectly increases Cl influx and stool volume
- softens stools
Reduces pain and bloating
Used only for ER TX of IBS (constipation) or chronic idiopathic constipation (CIC)
-emergency IND
Bismuth
For mild diarrhea
Antisecretory, antimicrobial, anti-inflammatory
SE - binds drugs, turns stool black
Opioids
Diphenoxylate-atropine
Not used commonly due to respiratory depression at high doses and RX doses cause dizziness, euphoria
Replaced by loperamide
